Abrasive tool



Jan. 20, 1948. E. D. TEAGUE 2,434,749

ABRASIVE TOOL Filed June 17, 1943 .Zzmvezzior V ZM V W Patented Jan. 20, 1948 ABRASIVE TOOL Ernest Douglas Teague, Welwyn Garden City,

England, assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Application June 1'7, 1943, Serial No. 491,195 In Great Britain June 25, 1942 2 Claims.

This invention relates to abrasive wheels or other tools of the type comprising diamond particles or granules (or other very hard particles) incorporated in a resinoid or other plastic bond. Diamond wheels or tools of the above type are often used in such a manner that the portion containing the diamond granules is worn unevenly, the tool often being considered unusable when only a fraction of the diamond-containing layer has worn through to the non-diamond-containing support or body. There are many cases where the grinding operation may lead to uneven or undue wear, including, for example, cup wheels for off-hand tool grinding where there is usually a tendency for wear to take place at a greater rate at the periphery due to the greater localized grinding pressure. Also cup wheels for use for tool grinding, and also for grinding small recesses at the back of the grinding edge of the tool known as the chip breaker, are subjected to a high rate of Wear at the outer portion and corner of the diamond-containing layer where high pressure is necessarily applied.

Undue wear is also liable to take place in resinoid or like bonded abrasive cutting off wheels as these wheels are liable to lose their cutting efficiency through the edge wearing to an approximately semi-circular or V-shape, which may cause a reduction in cutting speed or alternately a considerable increase in the rate of wear owing to the pressure applied to the narrow peak according to whether the original grinding action of the wheel is hard or soft. Tendencies to wear of the above character may sometimes be overcome or minimized by the use of a harder or more wear-resisting bond, e. g., a sintered metal powder bond, but where a soft bond of the resinoid or like type is desirable or essential no satisfactory solution of the Wearing problem has been found, and the aim of the present invention is to overcome the above difiiculties and to provide abrasive tools of the character indicated with reinforcement localized at or in the working face or layer, i. e., at or in the diamond granule (or like) bearing layer and more particularly in the vicinity of maximum wear of that layer.

The invention consists in a process of manufacturing abrasive wheels or other abrasive bodies having diamond or other abrasive material incorporated in a resinoid or other plastic bond, characterized by the feature that a metallic powder is incorporated in the abrasive bearing bond to form a hard localised wear-resisting skin or layer, in the vicinity of maximum wear of the abrasive wheel or body.

Other features of the invention are hereinafter fully described and claimed in the appended claims.

A suitable metallic powder consists of an iron known as electrolytic iron powder of, say, 300 mesh particle size, although satisfactory results may be obtained by using finely powdered tin, copper or other metal powders. The thickness of the skin may vary to some extent, an average thickness of the order of .005 being suitable.

The invention may be carried into effect in conjunction with an abrasive tool or wheel comprising resinoid, shellac or rubber bonds, or may be employed in connection with a bond of any of the plastics which are suitable for making abrasive tools.

Referring to the accompanying drawings, Figure 1 shows a sectional view of a mould with material therein ready for forming a cup wheel, while Figure 2 shows a section of the finished wheel.

In carrying the invention into effect according to one mode as described by way of example for the manufacture of a straight cup wheel (of the dimensions, for instance, of 3" x X /2" recessed on one side 2% x and having on the rim alayer of diamond granules bonded with a resinoid bond to a depth of 1%") a non-abrasive-containing premoulded form I is inserted in a mould band 5 together with a bottom plate 6 and arbor or aperture-forming member 1, the assembly being supported upon a fiat surface. The exposed inner surface of the mould band 5, that is to say the part adjacent and projecting beyond the upper surface of the premoulded form I is smeared evenly with an adhesive or grease, for example it may be treated with Voco Grease B. B. supplied by The Vacuum Oil Company. The purpose of providing this coating is to form a temporary supporting medium adapted to retain a quantity of loose metal powder which is subsequently applied. Instead of grease an adhesive such as glue or synthetic resin solution or the like may be satisfactorily employed for 10- eating and holding the metal powder. The preform I, bottom plate 6 and arbor l are then removed through the lower end of the mould band 5 and the upper rim or portion of the preform I is cleansed to remove any grease by the application of carbon tetrachloride or other suitable solvent.

The inner perlphery of the mould band 5 is now ready to receive the metal powder and accordingly a quantity of fine electrolytic iron powder of 300 mesh particle size is placed on the inner surface of the mould band, which is turned to rest on its circumference and rolled around in order that the metal powder will be distributed evenly over the whole of the grease coated area,

a substantial amount of the powder being reuncompresed diamond grain and bond mixture 2 which is subsequently to be introduced into the mould. The assembly, comprising the premoulded form I, mould band 5, bottom plate 6 and arbor l are then reinserted and a hub member 8 is placed in position. A suitable quantity of the diamond resinoid mixture 2 is positioned between the metal-loaded grease layer and the adjacent surface of the hub and levelled so that its upper surface lies slightly below (as above indicated) the upper edge of the metal-loaded grease layer 3, care being taken not to disturb the latter. A ring or annular pressure member 4 is then introduced between the mould band 5 and the hub member 8 and pressure applied in the usual manner.

After the pressing operation the completed article shown in Figure 2 is removed from the mould assembly and heat treated to cure the bond, oras is the usual practice with resinoid bonded diamond wheels-the article may be cured in the mould for approximately hr. at a temperature of 175 C. and then removed. In either case it will be found that the metal powder has impregnated the diamond-containing layer 2, forming a hard outer skin 3 (Figure 2). It may happen that a small quantity of grease and iron may spread on to the side surface of the diamondcontaining layer 2 from the periphery but this may be removed in the usual process of lapping this area on a cast iron plate with a 180 mesh silicon carbide grain, which also exposes the diamond grains for efficient operation.

Although the carrying of the invention into efiect has been described with reference to cup wheels, it will be appreciated that it may be equally satisfactorily carried into effect as applied to disc wheels carrying abrasives on the periphery, or on the sides, or on both the sides and the periphery, or to any other of the known forms of abrasive wheels. The invention may also be applied to honing sticks or stones where sometimes rapid wear on the corners or other localities may reduce the total life of the article.

It will be appreciated that the invention can also be satisfactorily carried into effect in the method of manufacture wherein the abrasive layer and the non-abrasive-containing support are moulded together simultaneously, i. e., without first moulding or moulding and curing the nonabrasive-containing support.

I claim:

1. The method of making an abrasive article which comprises supplying a thin layer of metal powder to a surface of a mold ring, filling the mold space contiguous to said metal powder with a mixture of abrasive grain and non-metallic bond, and heat treating the assembly causing the metal powder to impregnate the adjacent portion of the abrasive-bond composition and to form a hard surface thereon.

2. The process of manufacturing abrasive articles having abrasive material incorporated in a non-metallic bond characterized by the feature that a metallic powder is incorporated in the abrasive bearing bond by adhesively applyingit to the mold prior to introducing into the mold the mixture of abrasive and bond.

ERNEST DOUGLAS TEAGUE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,137,200 Boyer Nov. 15, 1938 2,145,888 Moulton et al. Feb. 7, 1939 2,162,600 Ball June 13, 1939 1,832,515 Webster Nov. 17, 1931 942,808 Baekeland Dec. 7, 1909 1,955,572 Adler et al. Apr. 17, 1934 1,422,200 Harris July 11, 1922 1,616,531 King Feb. 8, 1927 1,931,363 Stubbs Oct. 17, 1933 1,403,416 Katzenstein Jan. 10, 1922 

